A central problem for theories of memory development is how the superior memory of children and adults evolves from the memory abilities of infants and what mechanisms underlie this evolution. The paucity of data on infant long-term memory precludes a current solution. In this application, research is proposed that will narrow the large gap between what is known about long-term memory in children and adults and what is known about short-term visual recognition memory in infants. Three questions fundamental to the understanding of infant memory development will be addressed: (l) How do selective attention, perception, and differences in information processing affect what is encoded and retrieved at different ages? (2) How do new experiences interact with and modify prior memories, and what constrains these interactions at different ages? and (3) What are the consequences of retrieving memories for the subsequent accessibility and organization of their components? Answers will be achieved via two operant learning procedures we have developed to study learning and memory from 2-12 months. In both, infants learn a response that activates a distinctive toy (a crib mobile, a miniature train) in a distinctive context. Using a delayed recognition paradigm, we probe the contents of the newly acquired memory with a retrieval cue 1 or more days later. Infants indicate if the probe matches information in memory by performing the learned response; otherwise, they do not. Using a reactivation paradigm to obtain convergent evidence of our findings, we use the memory probe as a reminder after the memory is forgotten; subsequent testing with the original cue(s) indicates whether or not the reminder recovered the memory. The proposed research will extend our knowledge about normal memory development during infancy and will provide new insights regarding its relation both to memory processes of children and adults and to neuropsychological research on brain mechanisms implicated in memory formation. Finally, it will bridge the gap between memory processing in prelinguistic humans and in nonhuman animals. From a health perspective, the research will provide a standard for assessing early cognitive deficits--particularly those that require the utilization (retrieval) of accumulated, experienced-based information. The integration of the infant research with that from animals and human adults will be facilitated via extensive directed readings, interactions with experts in both fields, and participation in specialized conferences and seminars.